This invention relates to a lubricating oil composition containing a complex of a selected heterocyclic nitrogen compound and an oil soluble organometallic salt as a corrosion inhibitor.
The use of additives such as corrosion inhibitors in lubricating oil compositions has been widespread for a good many years. Some of the representative types of corrosion inhibitors used in lubricating oils are noted in "Lubricant Additives" by C. V. Smalheer and R. K. Smith, 1967, p. 6 and include metal dithiophosphates, metal dithiocarbamates, sulfurized terpenes and phosphosulfurized terpenes.
A variety of nitrogen containing compounds have been disclosed to be useful as corrosion inhibitors or as additives for other purposes in hydrocarbon compositions. U.S. Pat. No. 1,768,910 discloses the use of nitrogeneous base compounds such as pyridine, quinoline and piperidine as corrosion inhibitors in oil compositions. U.S. Pat. No. 2,060,138 discloses the combination of cyclohexylamine with various soaps to produce corrosion inhibitors for alcohol solutions. U.S. Pat. No. 2,296,342 discloses an oil composition with improved corrosion properties containing an oil soluble amine compound such as benzidine, toluidine and xylidine and an oil soluble ester of an acid. U.S. Pat. No. 2,468,163 discloses the use of cyclic amidines and in particular substituted imidazolines as corrosion inhibitors. U.S. Pat. No. 2,618,608 discloses the use of selected cyclic nitrogen compounds such as adenine as discoloration inhibitors in detergent compositions. U.S. Pat. No. 2,987,522 discloses the use of selected azaalkylene substituted cyclic amidines as corrosion inhibitors. U.S. Pat. No. 3,197,408 discloses synthetic ester lubricating oils with improved anti-corrosion properties containing selected nitrogen-containing heterocyclic compounds such as benzimidazole and cyanuric acid. U.S. Pat. No. 3,294,705 discloses the use of mixtures of selected aminoamides and salts of said aminoamides to inhibit corrosion in petroleum refining operations.
Other additives disclosed to be useful in lubricating oil compositions include: phosphatides as solubilizers for metal salts of carboxylic acids in U.S. Pat. No. 2,270,241; select copper and cobalt salts of organic acids in oils containing phenols to enhance the oxidation inhibition properties as shown in U.S. Pat. No. 3,018,248; and substituted benzodiazoboroles as oxidation inhibitors as disclosed in U.S. Pat. No. 3,481,978.
Despite the variety of known additives that are available, there is still the need and desire to find additional compounds having improved properties particularly as corrosion inhibitors in lubricating oil systems.